The present invention relates to a controller apparatus for a synchronous motor having a rotor, which is rotatably inserted within an inside of a stator wound with AC windings therein, as well as, a controlling method thereof, and in particular, it relates to the controller apparatus for fixing or locking the rotor when the synchronous motor is stopped, as well as, the controlling method thereof.
Conventionally, in case when driving a load, rotationally, such as, a pump, a fan or the like, for example, the frequency of the power source is changed through frequency conversion with using a frequency converter (so called, an inverter), thereby achieving the driving of the motor at a desired frequency thereof, as is already known in the following Patent Document 1, in particular, for rotationally driving the load, i.e., a refrigerator of a cryopump, etc., for example, at a predetermined rotation speed, with using a cryopump operating apparatus, which is built up with a driving apparatus made of a synchronous motor, while applying a commercial electric power source of 50 Hz therein.
On the other hand, as a synchronous motor for use of general-purposes, being a kind of an AC motor, there is already known a synchronous motor of multi-poles structure of applying a permanent magnet therein, as well as, that having a rotor constructed with windings wound around, or that having a rotor made of a permanent magnet; i.e., using the rotor, on a surface of which are formed grooves in plural numbers thereof, in the axial direction thereof, thereby forming tooth portions therearound. Further, such the rotor structure, having the tooth portions formed therearound in the structure thereof, is widely applied, for example, also in so-called a stepping motor, and in particular, due to the discovery of rear-earth magnets (i.e., neodymium, samarium/cobalt, etc.), each having a high antimagnetic force, in recent years, it comes to be applied further widely, since a higher torque can be obtain from the same construction or volume of the rotor, and therefore the rotor can be manufactured in mass-production, to be cheap relatively.
Patent Document 1: Japanese Utility-Model Publication No. Hei 1-14775 (1989).
By the way, as was mentioned above, in case when controlling voltage supplied to an induction motor and/or a synchronous motor for use of general-purposes, while applying an ordinary inverter therein, in general, it is the mainstream of adopting a control method, therein; i.e., keeping a V/F ratio (=φ) constant, for satisfying the rated load. For this reason, when stopping the synchronous motor, since the F (frequency of the supply voltage)=0, then it is common to change also the supply voltage V down to zero (0). Thus, the supply voltage to the synchronous motor goes down to zero (0) together with the frequency thereof, and therefore the rotor is not fixed in the position thereof, but can rotate freely. Then, according to the conventional art, for preventing the rotor from such the free rotation thereof, so-called a lock condition is prepared or provided therein, and with this is driven an electromotive lock mechanism, including a brake shoe therein, thereby to hold the rotor of the synchronous motor at a predetermined position.
However, in case where such the electromotive lock mechanism is provided within the synchronous motor, then the synchronous motor itself comes to be large in the sizes thereof, and it also comes to be an expensive one, due to complexity of the structures, including that lock mechanism therein.